Variable force impact printer with backspace mechanism

ABSTRACT

A single-elment printer having a complex drive cam for control of print impact velocity, employs power taken from the print shaft within the type element carrier to perform backspace operations as selected by the velocity control mechanism.

United States Patent Inventors William A. Abell,Jr.; [50] Field of 197/16, i7, Charles M. lsaacs; Jerome B. ODanlel, all 9 l 84, I57 of Lexington, Ky.

Appl. Nov 887,027

[56] References Cited UNITED STATES PATENTS 5/1968 Cralle,Jr.et l/l968 Hosey et al.

[22] Filed i 1 Dec. 22, 1969 Patented Nov. 9, 1971 l97/84 l97/9l l97/l 57 Assignee International Buslness Machines Corporation y w l u P a n e b O R r e m m m E w a n Armonk, N.Y.

Assistant ExaminerStephen C. Pellegrino Attorneys-Hamlin and Jancin and E. Ronald Coffman [54] VARIABLE FORCE IMPACT PRINTER WITH BACKSPACE MECHANISM 10 Claims, 3 Drawing Figs.

ABSTRACT: A single-elment printer having a complex drive cam for control of print impact velocity, employs power taken from the print shaft within the type element carrier to perform 197/17, l97/9l B41] 23/08,

backspace operations as selected by the velocity control mechanism.

[5i] Inl.Cl..

PATENTEUuuv 9 \sn sum 1 0F 2 INVENTORS.

WILLIAM A. ABELL,JR4 CHARLES M [SAACS JEROME B. O'DANIEL PATENTED 9 l9?! 3,618.7 36

SHEET 2 BF 2 FIG. 3

BACKGROUND OF THE INVENTION The primary function of a typewriter is to print characters. In addition, however, a typewriter must perform other ancillary functions such as backspacing, which are not directly related to the printing of characters. Traditionally, these ancillary functions have been maintained relatively independent of the primary print and space function of the typewriter. In-

herently, separation of the functions related to character printing, including letter spacing, from those functions not related to character printing, such as backspace, requires that separate power operating devices be employed to perform these functions. In addition, it has been necessary to provide interlock controls to prevent inconsistent simultaneous operation of the print-related and nonprint-related functions.

Print-related functions, such as word spacing and ribbon color shift, have been mechanically integrated with the primary printing function through the use of a print velocity control as disclosed respectively in US. Pat. Nos. 3,382,963 and 3,451,520. It is the object of the present invention to employ a print velocity selection mechanism to operate a nonprint-related function, namely backspace, to thereby eliminate the need for a separate power device and separate interlock controls for reliably performing the backspace function in a practical manner.

SUMMARY OF THE INVENTION This invention integrates mechanism for performing print function with mechanism for backspacing which is a nonprintrelated function, by providing a dual use of print velocity selection mechanism. Operation of the backspace mechanism is thus converted from a separate and distinct function into a simple variation of an ordinary print function. This invention thus simplifies both the direct structure for performing the backspace function and the indirect structure for interlocking between the backspace function and the print function.

Mechanical integration of the backspace and print functions is accomplished by the provision of the backspace drive cam that is cyclically rotated with the typewriter print shaft. A cam follower for driving the output of the backspace mechanism is normally ineffective to transmit motion between the backspace cam and the backspace output mechanism. A multiposition selector is employed to displace a cam follower to select various print velocities to thereby compensate for variations in character size. The selector can also obtain no velocity and thereby produce simple word spacing through the normal letter feed that ordinarily accompanies a print operation. Our invention controls this selector to a unique position wherein it renders the backspace cam follower connection effective. For most applications, this unique position also provides for a zero impact velocity of the type element to avoid an undesired print operation.

By use of our invention the backspace function can be selected by a fully interlocked portion of a typewriter keyboard like that described in U.S. Pat. No. 3,086,635 thus eliminating the need for separate interlocking and providing for a fully sequential cyclic operation of the print and backspace functions.

These and other objects, features, and advantages of our invention will be apparent to those skilled in the art from the following more specific description of an illustrative preferred embodiment of our inventive concepts, wherein reference is made to the accompanying drawings of which:

FIG. 1 is a fragmentary perspective view of a typewriter having a variable velocity print mechanism and a backspace mechanism constructed in accordance with our invention wherein for the sake of clarity, only the essential parts of the typewriter are shown;

FIG. 2 is an enlarged plan view of a velocity and backspace cam employed in the typewriter of FIG. I; and

FIG. 3 is an enlarged fragmentary plan view showing a detail of construction of the backspace mechanism employed in the typewriter of FIG. 1.

Referring now more specifically to the drawings, in FIG. 1 there is shown a typewriter or impact printer 10 of the type generally disclosed in US. Pat. Nos. 2,879,876 and 2,919,002.

The typewriter 10 is particularly characterized by its type or impact output device including a spherical type bearing element 11. The type element 11 presents selected types or character masters 12 to a printing position along a writing line 13 defined by an adjacent platen 14. A carrier 20 supports the type element 11 by a rocker member 21 that is pivoted to the carrier 20 by bearings 22 to enable the type element 11 to be driven into impact cooperation with the platen 14. The carrier 20 is movable along a track 15 conveniently provided as a secondary function of a rotatable print power shaft 16 and an escapement rack 17 both of which are supported by a frame 18. Normal printing operations are accompanied by incremental letter feed movement of the carrier 20 rightwardly along the printing line 13 under the control of an escapement mechanism not shown herein except for the escapement rack 17 and an escapement pawl 23 that is shown in FIG. 3. The details of an appropriate escapement mechanism are fully disclosed in aforesaid US. Pat. No. 3,059,751.

The typewriter 10 also includes a keyboard or data input means 30 that is constructed generally in accordance with aforesaid US. Pat. No. 3,086,635 to provide a reliable sequential cyclic control of the typewriter mechanism regardless of a relatively erratic rate of manipulation of individual keyboard keys. The keyboard 30 includes a backspace key button 31 as well as character key buttons, such as comma key 32 and W key 33 and a word space control key or space bar 34. Each of the keys 31, 32, 33, and 34 control a respective interposer 40, 41, 42, and 43 which functions to activate a cycle clutch 44 through control bail 44a to thereby initiate cyclic motion of a filter shaft 45 through and of the print shaft 16 through 360. Rotation of filter shaft 45 drives a selected interposer rightwardly. In the case of a printing key, such as comma key 32,- rightward motion of the associated interposer 41 functions to encode data for controlling rotation and tilt of the type element 11 to select the desired character for printing. The particular encoding is determined by a permutation of downward projections 46 on the interposer.

As disclosed in aforesaid US. Pat. No. 3,059,751 rotation of the filter shaft 45 also causes operation of the letter feed mechanism, not shown herein, to advance the carrier 20 one letter space increment in accompaniment with the printing of a character.

In addition to the selection of characters, it is also desirable to select a printing velocity that is coordinated with the area of individual characters to insure a uniform print density. US. Pat. No. 3,382,963 discloses one such'velocity or impact drive control mechanism, parts of which have been reillustrated herein. The impact drive control mechanism comprises a complex cam 60 that is mounted on a sleeve 24 which is slidably keyed to the print shaft 16 so as to be rotatable therewith. The cam 60 cooperates with a cam follower roller 50 that is connected through a rod 51 to a print output drive or motion transmitting link 52 that is pivoted to the carrier 20 about axis 53. A forked end 54 of the link 52 slidably receives a pin 25 connected to the rocker 21 for driving the type element 11 into impact cooperation with the platen 14.

The follower roller 50 is both slidably and rotatably mounted on its support rod 51 to be displaceable laterally of the cam 60 so as to cooperate with the cam 60 in four separate positions to thus provide for control of the impact drive. The components of the cam 60 are best seen in FIG. 2 where cam 60 has been enlarged to show its complex cam surface 60a more clearly. The cam 60 includes a high print velocity profile 61 having a high rise, a low print velocity profile 62 having a lesser rise than profile 61, a zero print velocity profile 63 having no substantial rise, a backspace cam profile 64 and a detent cam profile 65. The follower roller 30 is positionable into alignment with tracks 66 and 67 respectively on the cam profiles 61 and 62 and in alignment with two distinct tracks 68 and 69 on the profile 63. When the follower 50 is positioned adjacent the cam track 68 a space without print operation is generated. As hereinafter further explained, when cam follower 50 is positioned adjacent cam track 69 a backspace mechanism B is operated.

The mechanism for displacing the follower roller 50 along its support rod 51 comprises an operation selection control yoke 70 that receives the side edges of the roller 56 in a forklike cradle 71. The yoke is slidably supported on a rod 72 mounted in the carrier 20, and is biased rightwardly along the rod 72 by a spring 73. A closed loop motion transmission tape 80 is grounded on the carrier 20 by clip 26 and is traced around a frame mounted pulley 19 and a displaceable control pulley 81 to a hook 711a that is connected to the yoke 70. Control pulley 81 is mounted on an arm 82 that is pivoted to the frame 18 about an axis 820. Clockwise motion of arm 82 allows spring 73 to draw the yoke 70 and follower roller 51) rightwardly along their respective support rods 72 and ll.

Measurement of the displacement of yoke 70 is provided by four selectively operative stop members 96, 91, 92, and 93 which respectively select alignment of follower 50 with cam tracks 66, 67, 63, and 69 by arresting a cyclically moving bail 83 that controls arm 82. Bail 83 is pivoted about an axis rod 830 and carries a cam follower roll 34 that engages a double lobed cam 85 carried by the filter shaft 45. At the beginning of a cycle, cam 85 engages follower 84 at high dwell. Rotation of cam 35 clockwise with filter shaft 45 allows follower 34 to move leftwardly as urged by a spring 86. Counterclockwisc pivoting of bail 83 moves the am 82 through intermediate links 87, 88, and 89 clockwise. The distance through which ball 83 pivots counterclockwise is controlled by the selective positioning of the aforesaid stops 99, 91, 92, and 93.

Positioning of these stops is controlled by a pair of keyboard interposer operated bails 100 and 101. Bail 100 is pivotable counterclockwise and acts through connecting link 102 to pivot a stop plate 941 counterclockwise thus displacing the stop 91 to a position below the path of bail 83 where it is thus ineffective to arrest the bail. A bentover tab 95 on the stop plate 94 also displaces a stop plate 96 counterclockwise to thus move the stop 90 thereon downwardly below the path of bail 83. Accordingly, pivotal motion of bail 104) makes the stop 92 effective to arrest the bail 83. in a similar manner, bail 101 is pivotable to act on a stop plate 97 through a connecting link 103 to pivot the stop 92 downwardly out of the path of bail 83. Bentover tab 98 on the stop plate 97 again also carries the stop plate 96 counterclockwise to displace the stop 90 from the path of bail 83. Accordingly, pivotal motion of bail 101 makes stop 91 effective. If it is desired to render stationary frame mounted stop 93 effective, both bails 100 and 101 are pivoted to displace all stops 911, 91, and 92 from the path of bail 33. Finally, stop 90 will be effective whenever neither bail 100 or 101 has been pivoted.

Displacement of the bails 1110 and 101 is selected by the provision of appropriate operating projections 49 on the keyboard interposers. For example, since a large area character such as a W is to be printed with a high velocity, interposer 62 is provided with no projections 49. The stop 90 is thus left effective to select the cam track 66 on the high velocity cam profile 61. A low velocity is desired for small area characters such as the comma. Accordingly, a projection 49 is provided for displacing a tab 104 carried by the bail 101 to select the low velocity stop 91 thereby effecting positioning of follower 50 on cam track 67 on the low velocity profile 62. lnterposer 43, which is selected by the space bar 36, carries a projection 49 that displaces a tab 105 to pivot the bail 160 and thereby select stop 92 and the cam track 68. Finally, the backspace interposer 40 carries two projections 69 to displace tabs 106 and 107 that are respectively carried by the bails 100 and 101 thereby moving all movable stops 90, 91, and 92 out of the path of bail 83 and allowing the bail to move against fixed stop 93 to select the cam track 69.

To insure accurate positioning of the follower 50 a detent mechanism 74 is provided as described in aforesaid U.S. Pat. No. 3,382,963. This detent mechanism 74 includes a cam follower 75 that engages the detent cam 65 during rotation of print shaft 16 to pivot a toothed bar 76 away from a detent pawl 77 during the portion of the cycle that the yoke is being displaced along its rod 72. After the yoke 70 has been positioned to select one of the cam tracks 66, 67, 68 or 69, the detent cam 65 allows spring 78 to pull the toothed bar 76 against the detent pawl 77 thereby placing the pawl 77 in a selected tooth to positively define a precise position of the roller 50. Prior to the end of the cycle, cam follower is again driven by detent cam 65 to release the toothed bar 76 from the pawl 77 and permit the yoke 70 to restore to its home position as shown in FIG. 1. An alternative arrangement for positioning the roller 50 is described in IBM Technical Disclosure Bulletin Vol. 12 No. 7 at page l,032 entitled Print Velocity Control Device," Dec., 1969.

The backspace mechanism 13 comprises a backspace output pawl 110 (FIG. 3) that normally is engaged with teeth of the escapement rack 17 and is mounted on the carrier 20 by a plate 27 (see also P16. 1) and a post 111 that is received within a slot 110a in the backspace pawl 110. A spring 112, connected to the plate 27, biases the backspace pawl 110 leftwardly. The escapement pawl 23 is biased by a spring 28 into the teeth of the rack 17 and is pivotally mounted on the post 111 so as to hold the carrier 20 against rightward movement normally induced by a frame mounted carrier mainspring not shown. Letter feeding or rightward movement of the carrier 20 is accomplished by mechanism like that described in U.S. Pat. No. 3,059,751. During normal escapement operations, escapement pawl 23 is pulled out of engagement with rack 17. As escapement pawl 23 is pulled outwardly surface 23a on escapement pawl 23 contacts tab 110!) on backspace pawl 110 causing it to also be pulled from engagement with the rack. With both pawls out of the rack, carrier 20 is allowed to move rightwardly under the influence of the main spring until escapement pawl 23 reengages the rack. The pawls 23 and 110 are then reinserted into teeth of the rack 17 to arrest the carrier at an adjacent letter space position. The forward spacing mechanism thus described fonns no part of this invention. The backspace operation which is the essence of this invention is generated by forward movement of a drive link 113 (shown both in FIGS. 1 and 3) which causes clockwise pivoting of a bell crank 116 about an axis stud 115 that is fixed on the carrier plate 27. The rearward end 1140 of bellcrank 114 is dog legged downwardly at 11412 and carries a pin 116 that engages an escapement permitting slot 110C in the backspace pawl 110. Since the backspace pawl 110 is engaged with the stationary frame mounted rack 17, pin 116 cannot move laterally. Thus force applied to the drive link 113 will cause leftward motion of the stud 115 carrying with it the carrier 20. Escapement pawl surface 230 quickly moves leftwardly from under the backspace pawl tab 11Gb so that the backspace pawl 110 will not be lifted from the rack 17 when the normal lifting of the pawl 23 occurs later in the cycle. The escapement pawl 23 when reinserted into the rack 17 is ultimately allowed to drop by its bias spring 23 into the succeeding leftward tooth of the rack 17. Removal of the drive load from link 113 permits spring 112 to draw backspace pawl 119 leftwardly camming it also over a leftwardly disposed tooth and back to a position similar to that shown in FIG. 3, but wherein the carrier 21) is positioned one letter space to the left.

Operation of the drive link 113 is generated by a cam follower roller 117 that engages the backspace cam 64 and is controlled by an upstanding backspace control tab 79 that is carried by, and thus is responsive to the position of the operation selection control yoke 70. During each print operation, print shaft 16 will rotate to drive cam follower 117 rightwardly in F IG. 1. This motion will be ineffective to generate motion of the drive link 113 however, since the lower end 118 of a floating link 119 on which the follower roller 117 is mounted is free to waste the motion generated by the cam 64. When the follower yoke 71) is displaced to its backspace selecting position wherein the follower roller 50 tracks on cam track 69, upstanding tab 79 becomes aligned with the end 118 of the floating link 119. In this condition, rotation of print shaft l6 will cause pivoting of floating link 119 about the point of contact between tab 79 and end 118 thus generating a rightward or forward motion of the link 113 with a resultant operation of the backspace mechanism B.

By way of summary, a backspace operation is selected by depression of the backspace key 31 to activate interposer 40 and cycle clutch 44. lnterposer 40 will be driven rightwardly by filter shaft 45 and, through its two tabs 49, will pivot bails 100 and 101 counterclockwise. Counterclockwise pivoting of bails 100 and 101 causes selection of fixed stop 93 to thereby allow maximum displacement of the bail 83 and control arm 82 to permit rightward movement of the operation selection yoke 70 to align the cam follower 50 with cam track 69 (see FIG. 2). In this position backspace control tab 79 is also aligned with the lower end 118 of the floating lever 1 17. Rotation of print shaft 16 through the cycle clutch 44 allows detent cam follower 75 acting against detent cam 65 to be moved counterclockwise by its spring 78 thereby bringing the toothed bar 76 into engagement with the detent pawl 77 to retain the yoke 70 in its selected position. Further rotation of print shaft 16 drives floating link 119 clockwise about the stationary point now established between its end 118 and backspace control tab 79. Link 113 is thus driven forwardly to drive the carrier 20 lefiwardly through bell crank 114 and backspace pawl 110 thus performing the backspace operation. Rotation of shaft 16 does not drive rocker 21 through a print stroke since the follower S is tracking on cam profile 63 that has no substantial rise.

Those skilled in the art will recognize that the embodiment described herein is for the purpose of illustration only and various modifications, deletions, and additions can be made without departing from the novel concepts we have disclosed. Accordingly, the subject matter sought to be patented is defined solely by the appended claims.

We claim:

1. A printer having a frame, a platen mounted on said frame, a carrier type bearing means operably mounted on said carrier for movement into impact cooperation with said platen, track means mounted on said frame and movably supporting said carrier for movement along a writing line, and a rotatable power shaft connected with said carrier, wherein the improvement comprises:

impact drive control means mounted on said carrier and connected with said shaft and said type bearing means for selectively varying said impact cooperation, said impact drive control means including a control member, means mounting said control member for movement to a plurality of control positions, and means for displacing said control member to different ones of its control positions, backspace means mounted on said carrier, and

means operatively connected with said backspace means and responsive to positioning of said control member in one of said control positions to produce operation of said backspace means.

2. A printer having a frame, a platen, type bearing means, a carrier, means on said carrier for movably supporting one of said platen and said type bearing means for movement into impact cooperation with the other, track means mounted on said frame and movably supporting said carrier for movement along a writing line, and a rotatable power shaft connected with said carrier wherein the improvement comprises:

cam means mounted on said carrier and drivenly connected with said shaft, said cam means having a contoured cam surface,

cam follower means mounted on said carrier and cooperably engageable with said cam surface,

means for displacing said follower means relative to said cam surface for differential cooperation therewith,

print output means operably connecting said one of said platen and said type bearing means with said cam foilower means for efiecting said impact cooperation,

backspace means mounted in said carrier, and

means responsive to displacement of said follower means relative to said cam surface by said displacing means for selectively effecting operation of said backspace means.

3. A printer having a frame, a platen mounted on said frame, a carrier, type output means operably mounted on said carrier for movement into impact cooperation with said platen, track means mounted on said frame and movably supporting said carrier for movement along a writing line, and a lo rotatable power shaft connected with said carrier, wherein the improvement comprises:

cam means mounted in said carrier and drivenly connected with said shaft, said cam means having first and second cam profiles,

cam follower means mounted on said carrier and including a first cam follower operable by said first cam profile and interconnected with said type output means, and a second cam follower operable by said second cam profile,

backspace output means mounted on said carrier and connected with said second cam follower for operation thereby,

means mounting said cam means and said cam follower means for relative movement to a plurality of different mutual relative positions therebetween, and

operation selection means for effecting said relative motion for establishing an effective motion transmitting connection from said shaft through either of said first or second cam profiles to the respective one of said output means.

4. A printer as defined in claim 3 wherein:

said cam means further comprises a third cam profile having a lesser rise than said first cam profile, and

said first cam follower is selectively positionable by said operation selection means into operative relation with said type output means at respectively different ve|ocities.

5. A printer as defined in claim 3 wherein:

said cam means further comprises a third cam profile having no substantial rise thereon, and

said first cam follower is selectively positionable by said operation selection means into operative relation with either said first or said third cam profiles.

6. A printer having a frame, a platen mounted on said frame, a carrier, type bearing means operably mounted on said carrier for movement into impact cooperation with said platen, track means mounted on said frame and movably supporting said carrier for movement along a writing line, and a rotatable power shaft connected with said carrier, wherein the improvement comprises:

cam means mounted in said carrier and drivenly connected with said shaft, said cam means having a first cam profile having a substantial rise thereon, a second cam profile having no substantial rise thereon, and a third cam profile having a substantial rise thereon,

a first cam follower movably mounted on said carrier for positioning in either of two positions relative to said first and second cam profiles, said first cam follower being operatively aligned with said first cam profile in said first position and with said second cam profile in said second position,

means connecting said first cam follower with said type bearing means for driving said type bearing means into impact cooperation with said platen at a rate that is a direct function of the rise of said aligned cam profile,

backspace means mounted on said carrier and including backspace output means, a backspace cam drivenly connected to said shaft, and a backspace cam follower providing a selectively operative interengagement between said backspace cam and said backspace output means for performing a backspace operation, and

means responsive to positioning of said first cam follower in said second position thereof for rendering said backspace cam follower interengagement operative.

either said first or said third cam profiles for operating 7. A printer having a frame, a platen mounted on said frame, a carrier, type bearing means operably mounted on said carrier for movement into impact cooperation with said platen, track means mounted on said frame and movebly supporting said carrier for movement along a writing line, and a rotatable power shaft connected with said carrier, wherein the improvement comprises:

cam means mounted in said carrier and drivenly connected with said shaft, said cam means having a first cam profile having a substantial rise thereon, a second cam profile having no substantial rise thereon, and a third cam profile having a substantial rise thereon,

a first cam follower movably mounted on said carrier for positioning in any of three positions relative to said first and second cam profiles, said first cam follower being operatively aligned with said first cam profile in said first position and with said cam profile in said second and third positions,

means connecting said first cam follower with said type bearing means for driving said type bearing means into impact cooperation with said platen at a rate that is a direct function of the rise of said aligned cam profiles,

backspace means mounted on said carrier and including backspace output means, a backspace cam drivenly connected to said shaft, and a backspace cam follower providing a selectively operative interengagernent between said backspace cam and said backspace output means for performing a backspace operation, and

means responsive to positioning of said first cam follower in said third position thereof for rendering said backspace cam follower interengagcment operative.

8. An impact printer having a frame, track means mounted on said frame, a carrier movably supported on said track means for movement along a writing line, impact output means operatively mounted on said carrier, a rotatable power shaft connected with said carrier, data input means for defin ing individual items of print and nonprint information, and cyclicablly operable means responsive to said data input means for driving said power shaft through a predetermined increment of motion, wherein the improvement comprises:

cam means mounted in said carrier and drivenly connected with said shaft, said cam means having first and second cam profiles, backspace output means mounted on said carrier, cam follower means mounted on said carrier and including a first cam follower operable by said first cam profile and interconnected with said impact output means, and a second cam follower operable by said second cam profile and interconnected with said backspace output means, means mounting said cam means and said cam follower means for relative movement to a plurality of different mutual relative positions therebetween, and operation selection means responsive to said data input means for effecting said relative movement for establish ing an efiective motion transmitting connection from said shaft through either of said first or second cam profiles to the respective one of said output means. 9. An impact printer as defined in claim 8 wherein: said cam means further comprises a third cam profile having a lesser rise than said first cam profile, and said first cam follower is selectively positionable by said operation selection means into operative relation with either said first or said third cam profiles for operating said impact output means at respective different velocities. 10. An impact printer as defined in claim 8 wherein: said cam means further comprises a third cam profile having no substantial rise thereon, and said first cam follower is selectively positionable by said operation selection means into operative relation with either of said first or said third cam profiles.

1P B 0 8 n 

1. A printer having a frame, a platen mounted on said frame, a carrier type bearing means operably mounted on said carrier for movement into impact cooperation with said platen, track means mounted on said frame and movably supporting said carrier for movement along a writing line, and a rotatable power shaft connected with said carrier, wherein the improvement comprises: impact drive control means mounted on said carrier and connected with said shaft and said type bearing means for selectively varying said impact cooperation, said impact drive control means including a control member, means mounting said control member for movement to a plurality of control positions, and means for displacing said control member to different ones of its control positions, backspace means mounted on said carrier, and means operatively connected with said backspace means and responsive to positioning of said control member in one of said control positions to produce operation of said backspace means.
 2. A printer having a frame, a platen, type bearing means, a carrier, means on said carrier for movably supporting one of said platen and said type bearing means for movement into impact cooperation with the other, track means mounted on said frame and movably supporting said carrier for movement along a writing line, and a rotatable power shaft connected with said carrier wherein the improvement comprises: cam means mounted on said carrier and drivenly connected with said shaft, said cam means having a contoured cam surface, cam follower means mounted on said carrier and cooperably engageable with said cam surface, means for displacing said follower means relative to said cam surface for differential cooperation therewith, print output means operably connecting said one of said platen and said type bearing means with said cam follower means for effecting said impact cooperation, backspace means mounted in said carrier, and means responsive to displacement of said follower means relative to said cam surface by said displacing means for selectively effecting operation of said backspace means.
 3. A printer having a frame, a platen mounted on said frame, a carrier, type output means operably mounted on said carrier for movement into impact cooperation with said platen, track means mounted on said frame and movably supporting said carrier for movement along a writing line, and a rotatable power shaft connected with said carrier, wherein the improvement comprises: cam means mounted in said carrier and drivenly connected with said shaft, said cam means having first and second cam profiles, cam follower means mounted on said carrier and including a first cam follower operable by said first cam profile and interconnected with said type output means, and a second cam follower operable by said second cam profile, backspace output means mounted on said carrier and connected with said second cam follower for operation thereby, means mounting said cam means and said cam follower means for relative movement to a plurality of different mutual relative positions therebetween, and operation selection means for effecting said relative motion for establishing an effective motion transmitting connection from said shaft through either of said first or second cam profiles to the respective one of said output means.
 4. A printer as defined in claim 3 wherein: said cam means further comprises a third cam profile having a lesser rise than said first cam profile, and said first cam follower is selectively positionable by said operation selection means into operative relation witH either said first or said third cam profiles for operating said type output means at respectively different velocities.
 5. A printer as defined in claim 3 wherein: said cam means further comprises a third cam profile having no substantial rise thereon, and said first cam follower is selectively positionable by said operation selection means into operative relation with either said first or said third cam profiles.
 6. A printer having a frame, a platen mounted on said frame, a carrier, type bearing means operably mounted on said carrier for movement into impact cooperation with said platen, track means mounted on said frame and movably supporting said carrier for movement along a writing line, and a rotatable power shaft connected with said carrier, wherein the improvement comprises: cam means mounted in said carrier and drivenly connected with said shaft, said cam means having a first cam profile having a substantial rise thereon, a second cam profile having no substantial rise thereon, and a third cam profile having a substantial rise thereon, a first cam follower movably mounted on said carrier for positioning in either of two positions relative to said first and second cam profiles, said first cam follower being operatively aligned with said first cam profile in said first position and with said second cam profile in said second position, means connecting said first cam follower with said type bearing means for driving said type bearing means into impact cooperation with said platen at a rate that is a direct function of the rise of said aligned cam profile, backspace means mounted on said carrier and including backspace output means, a backspace cam drivenly connected to said shaft, and a backspace cam follower providing a selectively operative interengagement between said backspace cam and said backspace output means for performing a backspace operation, and means responsive to positioning of said first cam follower in said second position thereof for rendering said backspace cam follower interengagement operative.
 7. A printer having a frame, a platen mounted on said frame, a carrier, type bearing means operably mounted on said carrier for movement into impact cooperation with said platen, track means mounted on said frame and movably supporting said carrier for movement along a writing line, and a rotatable power shaft connected with said carrier, wherein the improvement comprises: cam means mounted in said carrier and drivenly connected with said shaft, said cam means having a first cam profile having a substantial rise thereon, a second cam profile having no substantial rise thereon, and a third cam profile having a substantial rise thereon, a first cam follower movably mounted on said carrier for positioning in any of three positions relative to said first and second cam profiles, said first cam follower being operatively aligned with said first cam profile in said first position and with said cam profile in said second and third positions, means connecting said first cam follower with said type bearing means for driving said type bearing means into impact cooperation with said platen at a rate that is a direct function of the rise of said aligned cam profiles, backspace means mounted on said carrier and including backspace output means, a backspace cam drivenly connected to said shaft, and a backspace cam follower providing a selectively operative interengagement between said backspace cam and said backspace output means for performing a backspace operation, and means responsive to positioning of said first cam follower in said third position thereof for rendering said backspace cam follower interengagement operative.
 8. An impact printer having a frame, track means mounted on said frame, a carrier movably supported on said track means for movement along a writing line, impact output means operatively mounted on said carrier, a rotatable power shaft connected with said carrier, data iNput means for defining individual items of print and nonprint information, and cyclicablly operable means responsive to said data input means for driving said power shaft through a predetermined increment of motion, wherein the improvement comprises: cam means mounted in said carrier and drivenly connected with said shaft, said cam means having first and second cam profiles, backspace output means mounted on said carrier, cam follower means mounted on said carrier and including a first cam follower operable by said first cam profile and interconnected with said impact output means, and a second cam follower operable by said second cam profile and interconnected with said backspace output means, means mounting said cam means and said cam follower means for relative movement to a plurality of different mutual relative positions therebetween, and operation selection means responsive to said data input means for effecting said relative movement for establishing an effective motion transmitting connection from said shaft through either of said first or second cam profiles to the respective one of said output means.
 9. An impact printer as defined in claim 8 wherein: said cam means further comprises a third cam profile having a lesser rise than said first cam profile, and said first cam follower is selectively positionable by said operation selection means into operative relation with either said first or said third cam profiles for operating said impact output means at respectively different velocities.
 10. An impact printer as defined in claim 8 wherein: said cam means further comprises a third cam profile having no substantial rise thereon, and said first cam follower is selectively positionable by said operation selection means into operative relation with either of said first or said third cam profiles. 